Walker Wholesale   1 800 824-2936
Auto Buyers. We make selling your car easy!
My "Check Engine" light is on. What does it mean?

It means your vehicle's onboard computer system has
self-diagnosed some kind of problem. The "Check Engine"
light, which is also called a "Malfunction Indicator Lamp" (MIL)
or "Service Engine Soon" (SES) lamp, is there to signal you
when a problem occurs that may require attention. This can
include anything from a momentary hiccup that has has little
or no noticeable affect on engine performance or driving safety
to a failure of a major electronic component.

There's no way to know what the light means without running
a diagnostic scan on the system to determine the nature of the
fault.

As a rule, a continuous Check Engine light usually signals a
"hard fault" or failure that has occurred. If the light comes on
and off, or only blinks momentarily, the problem may be
minor or intermittent in nature.

To help identify the problem, it helps to make a mental note of
the conditions that occurred when the light came on. Where
you driving at a certain speed? Accelerating or slowing down?
Shifting gears?

Onboard diagnostic systems are very complex and require a
fair amount of expertise as well as special tools to
troubleshoot. To find out what's wrong, a technician has to
"get into" your system through a diagnostic connector which
may be located under the dash, under the driver's seat or in
the engine compartment. The diagnostic connector serves as a
port of entry for accessing information and/or for putting your
vehicle's computer system into a special diagnostic mode for
further testing or displaying "fault codes".

Fault codes are numeric codes that are generated when a
problem is detected. If a sensor circuit reads out of range or
some electronic component fails to respond to a command
from the computer, the computer recognizes it as a fault and
records a number that corresponds to the nature of the
problem. The technician must then retrieve the code and refer
to specific diagnostic chart or "fault tree" that gives him the
step-by-step checks he has to perform to isolate the failed
component.

It can be a very time-consuming process depending on the
nature of the problem. Usually the process works but
sometimes it doesn't. An intermittent fault can be very difficult
to track down, and may require repeated attempts to repair it.
Back to Articles and Tips